The primary objective of this grant is to enhance and facilitate use of data from the Vietnam Era Twin Study of Aging (VETSA) for secondary analysis by archiving the data at the National Archive for Computerized Data on Aging (NACDA) at the Interuniversity Consortium for Political Science and Research (ICPSR). The VETSA is a nationwide longitudinal project designed to examine genetic and environmental influences on late midlife cognitive and brain changes. Starting in 2002, the baseline VETSA assessment conducted in-person testing of a community-dwelling sample of 1237 male twins ages 51-60 including a five- year follow-up completed in 2013. The project is unique in its inclusion of an in depth cognitive battery, magnetic resonance imaging data, neuroendocrine data, biomedical, biomarker, and psychosocial measures in the same middle-aged adults in the context of a behavior genetic study. We will achieve our primary objective as follows: Aim 1: We will apply new techniques associated with electronic documentation of social science data sets such as those developed by the Data Documentation Initiative (DDI-Lifecycle) to VETSA data. DDI- Lifecycle facilitates the creation of internet accessible social science data through the application of powerful programming languages such as electronic mark-up language (XML) in a format compliant with international archiving standards. Project-connected materials (e.g., procedures, codebooks, scoring systems, measures, variable definitions, statistical syntax, and datasets) will be documented and linked so as to facilitate interactive use by other researchers. Modern electronic archiving techniques expedite links within and between archived studies. Aim 2: Electronically documented VETSA materials will be placed at the NACDA/ICPSR archives where they can be easily accessed and disseminated through the internet. Aim 3: In addition to archiving data that are ready for analysis, we will create digital copies of actual on-paper responses of VETSA 2 participants (e.g., copies of drawn designs). By using up-to-date techniques for scanning and organizing documents in electronically searchable formats, these can be efficiently stored at the NACDA/ICPSR archives and easily retrieved by researchers. VETSA 1 on-paper records are already scanned and will be archived along with the VETSA 2 records. Access to original records and actual responses is immensely generative in that it allows future researchers to develop new techniques, approaches, and coding systems in ways never originally envisioned. The detailed electronic documentation proposed here is not part of the publicly available VETSA data, and the proposed project will provide the resources and infrastructure needed to implement the archiving. By making data structures easy to understand and easy to access, new generations of researchers can use the data for secondary analyses, thereby multiplying the National Institute on Aging's original investment in the VETSA. With our rapidly aging population, these data have potential for high public policy impact through the identification of risk and protective factors that may speed or delay cognitive and brain aging.